Improvements in or relating to artifical surfaces

ABSTRACT

An artificial surface 10, such as an artificial grass and/or sports surface 10, comprises a plurality of blades 5, and comprises a material or yarn 5 comprising a polyolefin or polymer material and at least one additive comprising a siloxane additive. Each of the blades 5 may be substantially straight. The artificial surface 10 may have a pile height of around 20 mm to 75 mm and/or a tuft gauge of at least ⅜ inch.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to UK Application No. 2209776.0filed Jul. 4, 2022, the disclosure of which is incorporated herein byreference in its entirety.

FIELD OF INVENTION

The present invention relates to a material or yarn for an artificialsurface, e.g., an artificial grass surface, a sports surface and/orsports playing surface. The present invention additionally oralternatively relates to a sports surface or sports playing surface oran artificial grass surface. The present invention also relates to amethod of manufacturing a material or yarn for an artificial surface,and to a method of manufacturing an artificial surface, such as anartificial grass/turf surface and/or sports (playing) surface, field orpitch.

BACKGROUND

Implementations of the present invention relate to a polyolefinartificial grass yarn developed for contact sports, by which is meantsports where an athlete/player/sports person makes body contact with anartificial grass yarn sports surface. This could be during a slide, atackle, scrummage or other such sports specific manoeuvres.

The artificial grass yarn of implementations of the present inventionhas been designed to reduce and/or eliminate incidence of skin injuries(commonly referred to as turf burns) to an athlete/player's skin. Theyarn can, therefore, be said to be “a skin friendly contact sportsyarn”.

There has an issue regarding skin injuries and artificial turf sinceartificial turfs inception in the 1960's. Nylon, polypropylene,polyethylene and other types of polyolefins have all been used in theproduction of artificial turf and have all caused skin injuries.

A skin injury or turf burn is commonly a combination of skin abrasionand a friction burn. Skin abrasion is a partial thickness wound causedby damage to the skin and can be in a range between superficial(involving only the epidermis) to deep (involving the deep dermis).Abrasions usually involve minimal bleeding. Mild abrasions—also known asgrazes or scrapes—do not scar or bleed because the dermis is leftintact, but deep abrasions that disrupt the normal dermal structures maylead to the formation of scar tissue. Abrasion injuries most commonlyoccur when exposed skin comes into moving contact with a rough surface,causing a grinding or rubbing away of the upper layers of the epidermis.

Friction burn is a form of abrasion caused by the friction of skinrubbing against a surface. As friction generates heat, extreme cases ofchafing may result in genuine burning of the outer layers of skin. Skinwill burn when it reaches 55-60° C. Burns that affect only thesuperficial skin layers are known as superficial or first-degree burns.They appear red without blisters and pain typically lasts around threedays. Injuries that extend into some of the underlying skin-layer arepartial-thickness or second-degree burns. Blisters are frequentlypresent, and such are often very painful. Healing can require up toeight weeks and scarring may occur.

While turf burns can happen on natural grass surfaces (1-3% playersreport skin injuries data from the SFA, UEFA and FIFA), the incidence ismuch higher on artificial grass sports surfaces (2.5-6% players reportskin injuries data from the SFA, UEFA and FIFA). It should also be notedthat due to the way skin injuries are recorded, this may be an underrepresentation of the true figure which could be higher.

Regardless of the numbers, players perceive turf burns as a real risk,which reduces acceptance of artificial surfaces for contact sports.Additionally, the fear of getting hurt by going to ground on theartificial surface is negatively influencing a player's performance andchanging their style of play to avoid injury.

Considering the present invention in terms of the problem/solutionapproach, the following comments are offered.

Players/athletes come into contact with a surface while performingsports specific manoeuvres, for example a sliding tackle in soccer orscoring a try in rugby, or by falling, being dragged or losing tractionon a surface.

During these constant surface contact events, a player could potentiallysuffer a turf burn—which is a skin injury caused by skin abrasion andheat from friction, as a moving object (player) moves quickly against animmobile object (surface).

These turf burns manifest as lacerations and blisters to the skin,sometimes several layers deep, potentially causing permanent scarring tothe skin.

The capacity for the skin to reach the temperature required for a turfburn, 55-60° C., is significantly higher on artificial grass sportssurfaces than it is on natural grass surfaces. This is because there isgreater friction between the skin and an artificial grass surface thanbetween the skin and a natural grass surface. This invention seeks toreduce this friction between the skin and the turf, hence reducing thecapacity for skin injury. Each player has unique skin conditions, and sotheir interaction with the surface will be unique. By reducing thefriction between the surface and the skin, one would reduce the risk ofskin injury.

Other influencing factors, aside from the type of surface, include:

-   -   (i) The skin care routine of the player—well-moisturised skin        tends to suffer less injury, and some players will apply a layer        of skin moisturiser prior to a match or game.    -   (ii) The presence of hair—more body hair reduces the risk as it        acts like a physical barrier.    -   (iii) The age of the player—older skin is more prone to injury.    -   (iv) Skin hydration level—higher hydration levels will suffer        less injury as it is more flexible and elastic.    -   (v) The wetness of the surface—a very dry surface will increase        the level of friction between the skin and the surface; some        pitch owners will water the surface with water prior to a game.

A number of documents disclose artificial playing surfaces. For example,GB2601243 (Stephen) discloses an artificial surface which isparticularly suited as a hockey playing surface. As such, the playingsurface of GB2601243 has functional requirements which may be differentfrom the requirements of artificial playing surfaces developed for othersports such as contact sports. For example, hockey playing surfaces arerequired to meet certain criteria for sports performance which arespecific to hockey, which are associated with structural features thatmay be different from, or even incompatible with, the requirementsand/or features of an artificial playing surface for contact sports. Forexample, hockey playing surfaces, typically requiring watering beforeuse, must allow the hockey ball to travel fast but minimise bounce,allow a player to get under the ball with their stick and provideconsistency of ball rolling and movement. This means hockey pitches tendto be free of infill material (sand or rubber), use texturised yarns,with filaments having a narrow tuft gauge (i.e. high pile density) ofaround 3/16″ and a low pile height of around 10-18 mm.

Various documents disclose examples of artificial surface, infill, ortreatment thereof, for example WO2020/142232A1 (Dow Global TechnologiesLLC) US2020/0121816A1 (Grossman), US2018/0016741A1 (Sirochman et al.),US2008/0124496A1 (Avery), U.S. Pat. No. 5,356,344 A (Lemieux), and GB0939053 A (Fabrication Ind De Moulage).

It may be an object of at least one embodiment of at least one aspect ofthe present invention to obviate or mitigate one or more disadvantagesor problems in the prior art.

It may be an object of at least one embodiment of at least one aspect ofthe present invention to provide an improved artificial surface, such asan artificial grass and/or sports (playing) surface.

SUMMARY OF INVENTION

According to the present disclosure there is provided: a material oryarn for an artificial surface, such as a sports/artificial grasssurface; an artificial surface; a sports field, pitch or court; a methodof manufacturing a material or yarn for an artificial surface; a methodof manufacturing an artificial surface; and use of a material or yarn inan artificial surface according to the appended claims.

A general solution of the present invention may be to alter a surfacetension of an artificial grass yarn used in production of an artificialsurface, e.g., sports field or pitch, so as to provide a more lubricatedfeel. In this way one can reduce friction which reduces horizontalvelocity, the sliding coefficient of friction and in doing so reducerisk of skin injury.

A key objective of the present invention is to reduce the coefficient ofdynamic friction on the surface while maintaining enough traction on thesurface so the player retains grip. This is achieved utilising anadditive (permanent slip additive). The specific additive exampleaccording to embodiments of the invention uses siloxane chemistry. Forexample, an additive containing Octamethylcyclotetrasiloxane (D4) CAS No556-67-2; EC No 209-136-7).

In this invention the addition of an additive (permanent slip additive)to the polymer acts to reduce the coefficient of dynamic friction—whichis defined as the force between two objects when one object is moving orif two objects are moving against one another. During processing, the(permanent slip) additive beneficially migrates to the surface as thepolymer material cools (because of incompatibilities with the basicpolymer). This may allow a (solid) lubricating layer to form. This mayact to lower the dynamic friction or adhesion between contactingsurfaces. Advantageously, the additive may not be chemically linked withthe (base) polymer but is retained in the polymer due to the additiveshigh molecular weight (and the resultant impaired mobility).

First Invention

According to a first aspect there is provided a material or yarn for anartificial surface, such as a sports surface or artificial grass/turfsurface.

The artificial surface may comprise or may be a contact sports playingsurface, e.g. a long pile contact sports playing surface.

The artificial surface may not comprise or may not be a short pile orhockey playing surface.

The material or yarn may comprise a synthetic turf or grass yarn.

The material or yarn may comprise a metallocene catalysed polyolefin orpolymer material. Metallocene-catalysed polyolefin/polymer offers anumber of advantages such as impact strength and/or robustness.

The material or yarn may comprise at least one additive comprising asiloxane additive.

The material or yarn may comprise a filament. The filament may be astraight or linear filament. The filament may be self-supporting, i.e.,capable of standing at least partially vertically unsupported. Thefilament may be a twisted filament or a straight twisted filament. Thefilament may be a monofilament or a slit film. The filament may have apropeller or diamond shaped cross-section. The filament may have across-sectional width of around 1.0 mm to 2.0 mm, e.g. 1.2 mm to 1.5 mm,and a cross-sectional breadth of around 200 μm to 450 μm, e.g. 300 μm to380 μm.

The provision of a straight or linear filament may be particularly wellsuited to the manufacture of an artificial playing surface for contactsports. Without wishing to be bound by theory, it is believed that usingstraight or linear filaments of any of the forms mentioned above,provides a larger smooth surface for the at least one additive, e.g.siloxane, to contact a player's skin, thus reducing friction andassociated risks of burns to the player. In contrast, the provision oftextured fibres or filaments, as typically found on hockey playingsurfaces, does not provide such a continuous smooth surface, andtherefore does not provide this advantageous effect. In addition, usingstraight or linear filaments, typically providing a longer pile height,may allow the use of infills within the playing surface which may helpreduce impact.

The polyolefin or polymer may comprise a polyolefin, e.g. polyethylene,such as linear low-density polyethylene (LLDPE).

The at least one additive may comprise or include (at least)Octamethylcyclotetrasiloxane (D4).

The at least one additive may comprise or include at least one of, ormay be selected from one or more of: Hexamethylcyclotrisilaxane (D3),Decamethylcyclopentasiloxane (D5), Dodecamethylcyclohexasiloxane (D6),Hexamethyldisiloxane (HMDS).

The polyolefin or polymer material may comprise 80% to 90% of thematerial or yarn.

The at least one additive may comprise 0.1% to 10% of the material oryarn, or to 5%, or beneficially 2% to 4%, e.g., 3% of the material oryarn.

The at least one additive may comprise or form a layer on the materialor yarn or on the polyolefin or polymer material (or polyolefin/polymermaterial or yarn core), such as an outer layer on the material or yarnor on the polyolefin or polymer material.

According to a second aspect there is provided an artificial surface,such as an artificial grass and/or sports surface.

The artificial surface may comprise or may be a contact sports playingsurface, e.g. a long pile contact sports playing surface.

The artificial surface may not comprise or may not be a short pile orhockey playing surface.

The artificial surface may comprise a plurality of (synthetic) blades.

Each blade may comprise a material or yarn comprising a synthetic turfor grass yarn comprising a metallocene catalysed polyolefin or polymermaterial and/or at least one additive comprising a siloxane additive.

The artificial surface may have a pile height of around 20 mm to 75 mm,e.g. 30 mm to 65 mm, e.g. 35 mm to 65 mm.

The artificial surface may have a tuft gauge of at least ⅜ inch (9.5mm), e.g. at least ½ inch (12.7 mm), e.g. at least ⅝ inch (15.9 mm),e.g. at least ¾ inch (19.0 mm). The artificial surface may have a tuftgauge of around ⅜ inch (9.52 mm), around ½ inch (12.7 mm), around ⅝ inch(15.9 mm), or around ¾ inch (19.0 mm). This is in contrast with thetypical tuft gauge of a hockey playing surface, which may be in theregion of around 3/16 inch (4.8 mm).

The artificial surface may comprise a (primary) backing material towhich the blades are woven or tufted.

The artificial surface may be provided with an infill material(s). Inone implementation the infill material(s) may comprise or may be aparticulate infill material, such as rubber, e.g. crumb rubber, and/orsand. In an alternative implementation, the infill material may betexturised yarns or filaments. For example, the texturised yarns orfilaments may be formed from a same material as the material or yarn ofthe first aspect of the present invention. The texturised yarns orfilaments may be woven or tufted to the backing material. In a furtheralternative implementation, no infill material may be provided.

Preferably, when an infill is used, the infill material(s) may compriseor may be a particulate infill material, such as rubber, e.g. crumbrubber, and/or sand. In such instance, the plurality of (synthetic)blades of the artificial surface may be straight or linear filaments,which may be selected from straight filaments, twisted filaments,straight twisted filaments, monofilaments, or slit film filaments. Thefilaments may have a propeller or diamond shaped cross-section. Thefilaments may have a cross-sectional width of around 1.0 mm to 2.0 mm,e.g. 1.2 mm to 1.5 mm, and a cross-sectional breadth of around 200 μm to450 μm, e.g. 300 μm to 380 μm.

The plurality of (synthetic) blades of the artificial surface may notinclude crimped or texturised yarns.

The provision of a straight or linear filament may particularly wellsuited to the manufacture of an artificial playing surface for contactsports. Without wishing to be bound by theory, it is believed that usingstraight or linear filaments of any of the forms mentioned above,provides a larger smooth surface for the at least one additive, e.g.siloxane, to contact a player's skin, thus reducing friction andassociated risks of burns to the player. In contrast, the provision oftextured fibers or filaments, as typically found on hockey playingsurfaces, does not provide such a continuous smooth surface, andtherefore does not provide this advantageous effect. In addition, usingstraight or linear filaments, typically providing a longer pile height,may allow the use of infills within the playing surface which may helpreduce impact.

The artificial surface may have a sliding coefficient of friction ofbetween 0.7 and 1.0, such as around 0.94.

According to a third aspect there is provided use of the material oryarn of the first aspect in an artificial surface, such as an artificialgrass or sports surface or playing surface, such as a field or pitch.

The use may comprise use of the material or yarn of the first aspect ina contact sports playing surface.

According to a fourth aspect there is provided a method of manufacturinga material or yarn according to the first aspect of the presentinvention.

The method may comprise:

-   -   providing a raw material (polyolefin or polymer material);    -   providing at least one additive;    -   extruding the raw material and the at least one additive so as        to form the material or yarn.

According to a fifth aspect there is provided a method of forming anartificial surface, such as an artificial grass and/or sports surface,according to the second aspect using filaments comprising the materialor yarn of the first aspect.

The method may comprise:

-   -   providing the material or yarn for the artificial surface;    -   tufting the material or yarn to a (primary) backing or        substrate.

The following optional features may apply to one or more of theforegoing first to fifth aspects of the present invention.

The material or yarn may comprise a synthetic turf or grass yarn.

The material or yarn may substantially comprise a polymer(ic) (base)material, e.g. a polyolefin or a polyamide. The polymer material maycomprise a polyolefin such as polyethylene or polypropylene, preferablypolyethylene. Alternatively the polymer material may comprise nylon.

The material or yarn may comprise at least one additive, for example, atleast one slip additive, preferably a permanent slip additive. A slipadditive may be an additive that can be added to polyolefin or polymermaterials to control/lower friction. A slip additive may be addeddirectly into a polyolefin or polymer material during an extrusionprocess and may migrate to a surface as the polyolefin or polymermaterial cools, thereby allowing a (solid) lubricating layer to form.

The at least one additive may comprise a further polyolefin or polymer.

The at least one additive may comprise or include a siloxane additive, asiloxane-based additive, and/or an additive that comprises a siloxanefunctional group.

The at least one additive may comprise or include an organosilicon, asilicone polymer or a silicone compound.

The at least one additive may comprise or include a cyclic siloxane.

The at least one additive may comprise or include a dimethylsiloxane ora cyclic dimethylsiloxane.

Preferably, the at least one additive may (at least or substantially)comprise or include Octamethylcyclotetrasiloxane (D4) (CAS No 556-67-2;EC No 209-136-7).

Alternatively or additionally, the at least one additive may comprise orinclude at least one of, or be selected from one or more of:Hexamethylcyclotrisilaxane (D3), Decamethylcyclopentasiloxane (D5),Dodecamethylcyclohexasiloxane (D6), Hexamethyldisiloxane (HMDS).

The siloxane additive may comprise an ultra-high molecular weight (UHMW)siloxane polymer. The siloxane additive may comprise an ultra-highmolecular weight (UHMW) siloxane polymer, which may be dispersed inthe/a polyolefin or polymer material, e.g., a low-density polyolefinmaterial, e.g., polyethylene (LDPE).

The at least one additive, e.g., (permanent) slip additive, may act toreduce the coefficient of (dynamic) friction p of the material or yarn.The coefficient of (dynamic) friction may be defined as the forcebetween two objects when the two objects are moving relatively againstone another.

Embodiments of the present invention may provide a material or yarnhaving an altered or engineered surface tension which may provide thematerial or yarn with an increased lubrication or lubrication feel

The material or yarn may comprise at least one further additive. The atleast one further additive may be selected from one or more of: a colourpigment(s), an ultraviolet light stabiliser and an anti-oxidant.

The at least one additive may comprise a layer on the material or yarnor on the polymeric base material, e.g. polyolefin material, preferablyan outer layer on the material or yarn or on the polyolefin material.The layer may be formed due to migration of the at least one additiveduring manufacture of the material or yarn, e.g., during a coolingprocess. The at least one additive may not be chemically linked to/withthe polyolefin or polymer (base) material. The at least one additive maybe retained in the polyolefin or polymer material due to a highmolecular weight (and resultant impaired mobility) of molecules of theat least one additive.

The provision of the at least on additive may beneficially selectivelycontrol/lower the coefficient of friction p of the material or yarn,e.g., an outer surface of the material or yarn. In this way slip orsurface friction of the material or yarn can be selectively controlled.

Advantageously, the material or yarn may be straight. The provision of astraight or linear filament may particularly well suited to themanufacture of an artificial playing surface for contact sports. Withoutwishing to be bound by theory, it is believed that using straight orlinear filaments of any of the forms mentioned above, provides a largersmooth surface for the at least one additive, e.g. siloxane, to contacta player's skin, thus reducing friction and associated risks of burns tothe player. In contrast, the provision of textured fibres or filaments,as typically found on hockey playing surfaces, does not provide such acontinuous smooth surface, and therefore does not provide thisadvantageous effect. In addition, using straight or linear filaments,typically providing a longer pile height, may allow the use of infillswithin the playing surface. The at least one additive may comprise or beprovided in pelletised form, e.g., as a masterbatch.

The at least one additive may comprise a slip additive.

The at least one additive may comprise a siloxane additive.

The siloxane additive may comprise an ultra-high molecular weight (UHMW)siloxane polymer, which may be dispersed in a low-density polyethylene(LDPE).

The at least one additive may form or comprise a layer on the materialor yarn or on the polyolefin material (or polyolefin material or yarncore), preferably an outer layer on the material or yarn or on thepolyolefin material.

The layer may be formed due to migration of the at least one additiveduring manufacture of the material or yarn, e.g., during a coolingprocess, e.g., subsequent to extrusion.

The artificial surface may comprise a sports (playing) surface.

The artificial surface may comprise a synthetic turf or grass surface orsystem.

Preferably the artificial surface may comprise or may be a contactsports playing surface. The artificial surface may not comprise or maynot be a hockey playing surface.

The (primary) backing or substrate may comprise a woven product. Thewoven product may comprise or be adapted to be used as a backing, suchas a primary backing or as a substrate layer, for example, for asurface, ground or floor covering such as artificial or synthetic grassor turf. The woven product may comprise at least a woven layer. Thewoven product may consist of the woven layer.

The woven layer may comprise weft tapes or threads and warp tapes orthreads.

The features described in the first to fifth aspects given hereinabovemay be provided in combination with the features as defined in the sixthto eighth tenth aspects given hereinbelow.

Second Invention

According to a sixth aspect there is provided an artificial surface,such as an artificial grass/turf and/or sports surface.

The artificial surface may comprise or may be a contact sports playingsurface.

The artificial surface may not comprise or may not be a hockey playingsurface.

The artificial surface may comprise a plurality of blades or filaments.

Each of the blades or filaments may be substantially straight or linear.The/each filament may be self-supporting, i.e., capable of standing atleast partially vertically unsupported.

The provision of a straight or linear filament may be particularly wellsuited to the manufacture of an artificial playing surface for contactsports. Without wishing to be bound by theory, it is believed that usingstraight or linear filaments of any of the forms mentioned above,provides a larger smooth surface for the at least one additive, e.g.siloxane, to contact a player's skin, thus reducing friction andassociated risks of burns to the player. In contrast, the provision oftextured fibres or filaments, as typically found on hockey playingsurfaces, does not provide such a continuous smooth surface, andtherefore does not provide this advantageous effect. In addition, usingstraight or linear filaments, typically providing a longer pile height,may allow the use of infills within the playing surface. Each blade orfilament may comprise a material or yarn comprising polymeric material,e.g. a polyolefin, and at least one additive comprising a siloxaneadditive.

Each blade may comprise a filament.

Each or one or more of the filaments:

-   -   may be substantially straight or linear;    -   may be self-supporting, i.e., capable of standing at least        partially vertically unsupported;    -   may be a twisted filament;    -   may be a straight twisted filament;    -   may comprise a monofilament or a slit film;    -   may have a propeller or diamond shaped cross-section; and/or    -   may have a cross-sectional width of around 1.0 mm to 2.0 mm or        1.2 mm to 1.5 mm and a cross-sectional breadth of around 200 μm        to 450 μm or 300 μm to 380 μm.

The polymeric material may comprise:

-   -   a polyolefin, e.g. polyethylene, such as linear low-density        polyethylene (LLDPE);    -   a metallocene-catalysed polyolefin and/or    -   a polyamide such as nylon.

The at least one additive may comprise or include (at least)Octamethylcyclotetrasiloxane (D4).

The at least one additive may comprise or include at least one of, ormay be selected from one or more of: Hexamethylcyclotrisilaxane (D3),Decamethylcyclopentasiloxane (D5), Dodecamethylcyclohexasiloxane (D6),Hexamethyldisiloxane (HMDS).

The polyolefin or polymer material may comprise 80% to 90% of thematerial or yarn.

The at least one additive may comprise 0.1% to 10% of the material oryarn, or to 5%, or beneficially 2% to 4%, e.g., 3% of the material oryarn.

The at least one additive comprises or forms a layer on the material oryarn or on the polyolefin or polymer material, such as an outer layer onthe material or yarn or on the polyolefin or polymer material.

According to a seventh aspect there is provided use of a material oryarn in an artificial surface, such as an artificial grass and/or sportssurface or playing surface, such as a field or pitch, wherein thematerial or yarn is substantially straight and comprises a material oryarn comprising a polyolefin or polymeric material and at least oneadditive comprising a siloxane additive.

The material or yarn may comprise a filament.

The filament:

-   -   may be a straight filament;    -   may comprise a monofilament;    -   may have a propeller or diamond shaped cross-section; and/or    -   may have a cross-sectional width of around 1.0 mm to 2.0 mm or        1.2 mm to 1.5 mm and a cross-sectional breadth of around 200 μm        to 450 μm or 300 μm to 380 μm.

The polymeric material may comprise a polyolefin, e.g. polyethylene,such as linear low-density polyethylene (LLDPE). The polymeric materialmay comprise nylon.

The at least one additive may comprise or include (at least)Octamethylcyclotetrasiloxane (D4).

The at least one additive may comprise or include at least one of, ormay be selected from one or more of: Hexamethylcyclotrisilaxane (D3),Decamethylcyclopentasiloxane (D5), Dodecamethylcyclohexasiloxane (D6),Hexamethyldisiloxane (HMDS).

The polyolefin or polymer material may comprise 80% to 90% of thematerial or yarn.

The at least one additive may comprise 0.1% to 10% of the material oryarn, or 0.5% to 5%, or beneficially 2% to 4%, e.g., 3% of the materialor yarn.

The at least one additive may comprise or form a layer on the materialor yarn or on the polyolefin or polymer material (or polyolefin/polymermaterial or yarn core), such as an outer layer on the material or yarnor on the polyolefin or polymer material.

The artificial surface may comprise a (primary) backing material towhich the blades are woven or tufted.

The artificial surface may be provided with an infill material(s), Inone implementation the infill material(s) may be crumb rubber and/orsand. In an alternative implementation, the infill material may betexturised yarns or filaments. For example, the texturised yarns orfilaments may be formed from a same material as the material or yarn ofthe first aspect of the present invention. The texturised yarns orfilaments may be woven or tufted to the backing material. In a furtheralternative implementation, no infill material may be provided.

According to an eighth aspect there is provided a method of forming anartificial surface according to the sixth aspect of the presentinvention using the material or yarn of the seventh aspect.

The method may comprise:

-   -   providing the material or yarn;    -   tufting the material or yarn to a (primary) backing or substrate        so as to form the artificial surface.

The following optional features may apply to one or more of theforegoing first to fifth aspects of the present invention.

The artificial surface may comprise a sports (playing) surface.

The artificial surface may comprise at least one and preferably aplurality of materials or yarns for an artificial surface, such as asports surface.

The material(s) or yarn(s) may be tufted to a (primary) backing.

The material or yarn may comprise a synthetic turf or grass yarn.

The material or yarn may substantially comprise a polyolefin or polymermaterial.

The polymer material may comprise a polyolefin, preferably polyethylene,or alternatively may comprise nylon.

The material or yarn may comprise at least one additive, for example, atleast one slip additive, preferably a permanent slip additive.

The at least one additive may comprise or include a siloxane-basedadditive.

The method may comprise:

-   -   providing a raw material (a polymer, e.g. a polyolefin);    -   providing at least one additive;    -   extruding the raw material and the at least on additive so as to        form the material or yarn.

The at least one additive may comprise be provided in pelletised form,e.g., as a masterbatch.

The at least one additive may comprise a slip additive.

The at least one additive may comprise a siloxane additive.

The siloxane additive may comprise an ultra-high molecular weight (UHMW)siloxane polymer, which may be dispersed in a low-density polyethylene(LDPE).

The at least one additive may form or comprise a layer on the materialor yarn or on the polyolefin material (or polyolefin material or yarncore), preferably an outer layer on the material or yarn or on thepolyolefin material.

The layer may be formed due to migration of the at least one additiveduring manufacture of the material or yarn, e.g., during a coolingprocess, e.g., subsequent to extrusion.

The (primary) backing or substrate may comprise a woven product. Thewoven product may comprise or be adapted to be used as a backing, suchas a primary backing or as a substrate layer, for example, for asurface, ground or floor covering such as artificial or synthetic grassor turf. The woven product may comprise at least a woven layer. Thewoven product may consist of the woven layer.

The woven layer may comprise weft tapes or threads and warp tapes orthreads.

It will be appreciated that any features of any of the aforementionedaspects may be used either singly or in combination with any otherfeatures of any of the aforementioned aspects.

The features defined in the sixth to eighth aspects given hereinabovemay be provided in combination with the features as defined in the firstto fifth aspects given hereinabove.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the present invention will now be described by way ofexample only, and with reference to the accompanying drawings, whichare:

FIG. 1 a schematic view of an extrusion apparatus used in themanufacture of a material or yarn for an artificial surface according tothe present invention;

FIG. 2(a) a schematic view of a tufting process used in the manufactureof the material or yarn for an artificial surface according to thepresent invention;

FIG. 2(b) a schematic view of the tufting apparatus used in themanufacture of the material or yarn for an artificial surface accordingto the present invention;

FIGS. 3(a) to (c) a schematic sectional top view and a schematicsectional side views of a (primary) backing for use in an embodiment ofan artificial surface according to the present invention;

FIG. 4 a schematic perspective view of a plurality of blades, filamentsor yarns comprise a tuft of synthetic grass according to an embodimentof the present invention;

FIGS. 5(a) and (b) a perspective view from above and to one side and aperspective view from below and to one side of an artificialsurface/grass/turf according to an embodiment of the present inventioncomprising the material or yarn according to FIG. 4 ;

FIG. 6 a perspective view from above and to one side of the artificialsurface of FIG. 5(a) including infill materials;

FIG. 7 a test rig for testing the artificial surface of FIG. 5(a)

FIG. 8 a schematic perspective view of a plurality of blades, filamentsor yarns comprising a tuft of synthetic grass according to a furtherembodiment of the present invention;

FIG. 9 a perspective view from above and to one side of an artificialsurface/grass/turf according to another embodiment of the presentinvention comprising a plurality of tufts according to FIG. 8 .

DETAILED DESCRIPTION OF DRAWINGS

Referring to FIGS. 1 to 7 , there will be described a material or yarn,generally designated 5, for an artificial surface 10, such as a sportssurface, for example, a sports playing surface, according to anembodiment of the present invention. There will also be described amethod of manufacturing the material or yarn 5, the artificial surface10 comprising the material or yarn 5, and a sports field, pitch or courtor play/playing area, such as a field or pitch, comprising theartificial surface 10.

Herein the following terms are to be generally understood as follows:

Extrusion process: a means by which polyolefin raw materials by means ofheat are melted and combined with other polyolefin additives, forinstance colour additives, to form a homogenous mixture and be made intoa new form.

Grass yarn: a synthetic fibre, a plurality of such forming a surfacemade to look like natural grass.

Monofilament yarn: a type of artificial grass yarn produced by extrudingmolten polymeric materials through a die to produce continuous strands.

Synthetic surface: an overall system, which comprises a sub-base,drainage, potentially a shockpad, and an artificial grass surface orcarpet, and often an infill material(s) which sits between the grassyarn to keep such in place and assist in specific performancerequirements.

Referring to FIG. 4 , according to an embodiment of the presentinvention, there is provided a material or yarn 5 for an artificialsurface 10 or carpet, such as a sports surface.

The material or yarn 5 comprises a synthetic turf or grass yarncomprising a metallocene catalysed polyolefin or polymer material and atleast one additive comprising a siloxane additive.

The material or yarn comprises a filament which:

-   -   is a straight or linear filament;    -   is a twisted or straight twisted filament;    -   is self-supporting, i.e., capable of standing at least partially        vertically unsupported;    -   is a monofilament;    -   has a propeller or diamond shaped cross-section; and/or    -   has a cross-sectional width of around 1.0 mm to 2.0 mm or 1.2 mm        to 1.5 mm and a cross-sectional breadth of around 200 μm to 450        μm or 300 μm to 380 μm.

The material or yarn 5 comprises a synthetic turf or grass yarn. Thematerial or yarn 5 substantially comprise a polyolefin (base) material.In this embodiment, the polyolefin material comprises polyethylene,e.g., low-density polyethylene (LDPE), beneficially linear low-densitypolyethylene (LLDPE).

The material or yarn 5 comprise at least one additive, for example, atleast one slip additive, preferably a permanent slip additive. The atleast one additive can comprise a further polymer. In this embodiment,the at least one additive comprises or includes a siloxane additive, asiloxane-based additive, and/or an additive that comprises a siloxanefunctional group.

The at least one additive can comprise or include an organosilicon, asilicone polymer or a silicone compound. The at least one additive cancomprise or include a cyclic siloxane. The at least one additive cancomprise or include a dimethylsiloxane or a cyclic dimethylsiloxane.

Advantageously, the at least one additive comprises or includes (atleast) Octamethylcyclotetrasiloxane (D4) (CAS No 556-67-2; EC No209-136-7).

Alternatively or additionally, the at least one additive comprises orincludes at least one of, or is selected from one or more of:Hexamethylcyclotrisilaxane (D3), Decamethylcyclopentasiloxane (D5),Dodecamethylcyclohexasiloxane (D6), and/or Hexamethyldisiloxane (HMDS).

The siloxane additive can comprise an ultra-high molecular weight (UHMW)siloxane polymer. The siloxane additive can comprise an ultra-highmolecular weight (UHMW) siloxane polymer, which may be dispersed inthe/a polyolefin material, e.g., a low-density polyolefin material,e.g., polyethylene (LDPE).

The at least one additive, e.g., (permanent) slip additive, may act toreduce the coefficient of (dynamic) friction of the material or yarn.The coefficient of dynamic friction may be defined as the force betweentwo objects when the two objects are moving relatively against oneanother.

Embodiments of the present invention provide a material or yarn havingan altered or engineered surface tension which can provide the materialor yarn with an increased lubrication or lubrication feel.

The material or yarn comprises a monofilament.

The polyolefin material comprises 80% to 90% of the material or yarn.

The at least one additive comprises 0.1% to 10% of the material or yarn,or 0.5% to 5%, or 3% of the material or yarn.

The material or yarn can comprise at least one further additive.Typically, the at least one further additive can be selected from one ormore of: a colour pigment(s), an ultraviolet light stabiliser and ananti-oxidant.

Beneficially, the at least one additive comprises a layer on thematerial or yarn or on the polyolefin material (or polyolefin materialor yarn core), preferably an outer layer on the material or yarn or onthe polyolefin material. The layer can be formed due to migration of theat least one additive during manufacture of the material or yarn, e.g.,during a cooling process.

Referring to FIG. 1 , according to the present invention, there isprovided a method of manufacturing a material or yarn 5 for anartificial surface 10, the method comprising:

-   -   providing a raw material;    -   providing at least one additive;    -   extruding the raw material and the at least on additive so as to        form the material or yarn 5.

The at least one additive is typically provided in pelletised form,e.g., as a masterbatch.

The at least one additive can comprise a slip additive.

The at least one additive can comprise a siloxane additive.

The siloxane additive can comprise an ultra-high molecular weight (UHMW)siloxane polymer, which can be dispersed in a low-density polyethylene(LDPE), e.g., linear low-density polyethylene (LLDPE).

Beneficially, the at least one additive forms or comprises a layer onthe material or yarn 5 or on the polyolefin material (or polyolefinmaterial or yarn core), advantageously an outer layer on the material oryarn or on the polyolefin material. The layer can be formed due tomigration of the at least one additive during manufacture of thematerial or yarn, e.g., during a cooling process, e.g., subsequent toextrusion.

Referring to FIGS. 4 to 6 , according to the present invention there isprovided an artificial surface 10 comprising at least one, andbeneficially a plurality, of materials or yarns 5.

The artificial surface 10 comprises a sports (playing) surface, and inparticular a contact sports (playing) surface. It will be appreciatedthat, as explained above, the requirements and structure of contactsports playing surface may be different from other types of payingsurfaces such as hockey surface.

The artificial surface typically comprises a synthetic turf or grasssurface or system.

According to the present invention there is provided a sports field,pitch or court, or a play/playing area, comprising the artificialsurface 10. Referring to FIGS. 2(a) and 2(b), according to the presentinvention, there is provided a method of manufacturing the artificialsurface 10, the method comprising:

-   -   providing the material or yarn 5 for the artificial surface 10;    -   tufting the material or yarn 5 to a (primary) backing or        substrate 15.

The material or yarn 5 is provided according to the method hereinbeforedescribed.

The (primary) backing or substrate 15 comprises a woven product. Thewoven product comprises or is adapted to be used as a backing, such as aprimary backing or as a substrate layer, for example, for a surface,ground or floor covering such as artificial or synthetic grass or turf.The woven product can comprise at least a first woven layer 20.

The woven product can consist of the single first woven layer 20 (seeFIGS. 3 (a) to 3(c)).

The first woven layer 20 can comprise a plurality of warp tapes orthreads 30 and a plurality of weft tapes or threads 35, the warp tapesor threads 30 and the weft tapes or threads 35 of the first woven layerbeing substantially perpendicular to one another.

The artificial surface 10 comprises at least one and preferably aplurality of materials or yarns 5.

The material(s) or yarn(s) 5 are tufted to (primary) backing 15.

Herein described is a method of manufacturing a material or yarn 5 foran artificial surface 10.

The method can comprise:

-   -   providing a raw material;    -   providing at least one additive;    -   extruding the raw material and the at least on additive so as to        form the material or yarn 5.

Herein described is a sports field, pitch or court, or a play/playingarea, e.g. a contact sports playing surface, comprising an artificialsurface 10.

Herein described is a method of manufacturing an artificial surface, themethod comprising:

-   -   providing 5 material or yarn 5;    -   tufting the material or yarn to a primary backing or substrate        15.

Herein described is an artificial surface 10, such as an artificialgrass and/or sports surface, the artificial surface comprising aplurality of blades 7, wherein each of the blades comprises a materialor yarn 5 comprising a synthetic turf or grass yarn comprising a polymermaterial and at least one additive comprising a siloxane additive. Thepolymer material is preferably a metallocene-catalysed polyolefin.

The artificial surface has a pile height of around 20 mm to 75 mm, e.g.30 mm to 65 mm, e.g. 35 mm to 65 mm. The artificial surface also has atuft gauge of at least ⅜ inch (9.5 mm), e.g. at least ½ inch (12.7 mm),e.g. at least ⅝ inch (15.9 mm), e.g. at least ¾ inch (19.0 mm).Typically, the artificial surface has a tuft gauge of around ⅜ inch(9.52 mm), around ½ inch (12.7 mm), around ⅝ inch (15.9 mm), or around ¾inch (19.0 mm). This is in contrast with the typical tuft gauge of ahockey playing surface, which may be in the region of around 3/16 inch(4.8 mm).

In some embodiments, the artificial surface is provided with one or moreinfill materials, which in this embodiment is crumb rubber, asillustrated in FIG. 6 .

The artificial surface 10 typically has a sliding coefficient offriction between 0.7 and 1.0, such as around 0.94.

Herein described is the use of the material or yarn 5 in an artificialsurface 10, such as an artificial grass or sports surface or playingsurface such as a field or pitch.

Herein described is a method of manufacturing a material or yarn 5, themethod comprising:

-   -   providing a raw material;    -   providing at least one additive;    -   extruding the raw material and the at least one additive so as        to form the material or yarn.

Herein described is a method of forming an artificial surface, such asan artificial grass and/or sports surface using filaments comprising thematerial or yarn 5, the method comprising:

-   -   providing the material or yarn 5 for the artificial surface 10;    -   tufting the material or yarn 5 to a (primary) backing or        substrate 15.

Herein described is an artificial surface 10, such as an artificialgrass and/or sports surface, the artificial surface 10 comprising aplurality of blades or filaments 7, wherein each of the blades orfilaments 7 is substantially straight and comprises a material or yarn 5comprising a polyolefin or polymer material and at least one additivecomprising a siloxane additive.

The provision of a straight or linear filament may particularly wellsuited to the manufacture of an artificial playing surface for contactsports. Without wishing to be bound by theory, it is believed that usingstraight or linear filaments of any of the forms mentioned above,provides a larger smooth surface for the at least one additive, e.g.siloxane, to contact a player's skin, thus reducing friction andassociated risks of burns to the player. In contrast, the provision oftextured fibers or filaments, as typically found on hockey playingsurfaces, does not provide such a continuous smooth surface, andtherefore does not provide this advantageous effect. In addition, usingstraight or linear filaments, typically providing a longer pile height,may allow the use of infills within the playing surface. Hereindescribed is the use of a material or yarn 5 in an artificial surface10, such as an artificial grass and/or sports surface or playingsurface, such as a field or pitch, wherein the material or yarn 5 issubstantially straight and comprises a material or yarn comprising apolyolefin or polymer material and at least one additive comprising asiloxane additive. The material or yarn is beneficially capable of beingself-supported, i.e., capable of at least partially standing in avertical disposition akin to a blade of natural grass.

The present invention provides a method of forming an artificial surface10 using the material or yarn 5, the method comprising:

-   -   providing the material or yarn 5;    -   tufting the material or yarn 5 to a (primary) backing or        substrate 15 so as to form the artificial surface 10.

Specific embodiments and examples of the present invention will now bedescribed in further detail.

Process Extrusion Process

Referring to FIG. 1 , there is shown an extrusion apparatus, generallydesignated 100, for forming the yarn 5. Inter alia, the extrusionapparatus 100 comprises an extruder 115, a heated die 105, and a waterbath 110.

The permanent slip additive—which is non migratory—is incorporated intothe synthetic grass yarn 5 during the extrusion process.

Synthetic grass yarns 5 in this application are produced viamonofilament extrusion or slit film extrusion. In these processes, rawmaterial of polyethylene polymer pellets (dosage 80-90%), combinationmasterbatch—which contains colour pigments, ultra-violet lightstabilisers and antioxidants in a carrier resin—(dosage 5-10%), apolymer process aid (dosage 0.2-1%) and a masterbatch containing slipadditive (dosage 0.1-10%), form the recipe.

These materials are all dosed in precise amounts according to the recipeinto the extruder 115. The extruder 115 is a heated barrel whichcontains a screw. The materials drop into the heated barrel (entersbarrel in excess of 200° C.) containing the screw and the screw startsto transport the material, during this transportation the heat and theaction of the screw cause the material to melt and mix together into ahomogeneous mixture. At the end of the extruder 115 are a set of filterswhich remove any degraded or oversized material, the molten homogenousmixture is transported to the heated die 105 (heated in excess of 200°C.) which contains plates with holes which the material is forced out ofinto a water bath to quickly cool the molten mixture into continuousfilament/yarn like forms—these are called monofilaments. Alternatively,the material is pushed through a coat hanger die and formed into a sheet(width of the sheet can vary from 0.9-2.5 m). The sheet is quicklycooled by either water bath or chill roll.

In the monofilament process the holes in the plates are homogenous insize and shape, for example, propeller or diamond shape, so that eachmonofilament is identical. Once these monofilaments or the sheet arecooled in the water bath 110 or chill roller (below 40° C.), such aretransported to a drying section; here the water is removed from themonofilaments or sheet.

During the slit film process after drying the sheet is slit into tapes(between 5-40 mm width) before it can go to the next stage.

After drying, the filaments and/or tapes can start to be drawn andannealed. In the drawing section the monofilaments/tapes are stretchedusing an oven (heated in excess of 80° C.) in the machine direction thisgives the monofilaments/tapes strength. In the slit film process thetapes are fibrillated to increase the flexibility of the tape fortufting and to make the tape appear more natural in appearance.

The monofilaments/tapes are then heated (in excess of 80° C.) and thenannealed in their new form. In the final section the monofilaments/tapesare cooled (below 40° C.) and an application of spin oil (0.1-1% w/v) isapplied via a lick roller.

In the monofilament process, the monofilaments are grouped intomonofilament bundles and are collected onto spools for the next stage ofthe process. In the slit film process each tape is individuallycollected onto spools for the next stage of the process.

Twisting/Spiral Wrapping Process

In order to ease downstream processing of the yarns 5, thefilaments/tapes are either twisted or spirally wrapped to make the yarna round shape. This assists in threading the yarns through the tuftingmachine tubes and needles.

Twisting involves taking the filaments/tapes and twisting on nedirection either “S”—left hand twist, or “Z” right hand twist. The twistis usually described as the number of turns per meter (TPM), commonlyfrom 20-40 TPM. The twisted yarn is then conveyed onto a spool in eithera precision or crosswound pattern.

Spiral wrapping the filaments/tapes also performs the same function astwisting, but instead of twisting the filaments/tapes into a round shapethe yarns are wrapped with a draw-textured-yarn (DTY) commonly polyesterthough other materials can be used. The number of spiral wraps can bebetween 20-60 wraps per meter.

The spirally wrapped yarn is then conveyed onto a spool in either aprecision or crosswound pattern.

Tufting Process

Referring to FIGS. 2(a) and (b), there is shown a tufting process and atufting apparatus, generally designated 300. FIGS. 3(a) to 3(c) shows abacking 15 for an artificial surface 10 according to an embodiment ofthe present invention.

In the tufting process, the carpet construction is described by threeparameters: stitch rate—defined as the number of stitches over a givenlength; pile height—the length of the stitch protruding from the primarybacking cloth; and tuft gauge—which is the distance between the tuftingneedles, commonly described in fractions of an inch. Less descriptive isthe pile weight, which is the weight of the carpet per square meterwhich can range from 750 g/m² to over 5000 g/m². During tufting, goodtension control on the yarn 5 to ensure consistency to the tuftingneedles and sharp blades are required to cut the pile length to thecorrect height, followed by consistent heat application in the coatingprocess. All this should give evenness and surface consistency to thefinal synthetic grass surface. This is referred to commonly as the grasscarpet.

The composition of the carpet can take many forms, from long pile carpetinfilled with a ballast or first infill material 12 a (commonly roundsilica sand) and a second (performance) infill material 12 b, whichcould be SBR rubber from end-of-life tires, EPDM, TPE, organic infills(such as cork, coconut husk, walnut shells etc.) as well as manycommercially available infills.

The carpet is commonly filled with the infill materials 12 a, 12 b belowthe level of the grass fibre. For example, a carpet with a pile heightof 55 mm may have an infill level between 35 mm to 50 mm.

Another example is a carpet without any infill materials as describedabove. In this non-infill variant, the space the infill would have takenup is replaced by an alternate material, commonly a texturizedmonofilament artificial grass yarn, but could also be a slit film yarn.

In this instance the secondary yarn is introduced to the carpet duringthe tufting process. The secondary yarn is threaded into the needles inthe required pattern and tufted with the primary yarn.

Both types of grass carpet are used in sports pitches where skininjuries can occur.

Supporting Data Samples Tested

Two artificial grass yarns were converted into artificial grass carpets,according to the embodiment of FIGS. 4 to 6 :

-   -   Yarn 1—control sample—containing no slip additive.    -   Yarn 2—yarn subject of the present invention containing slip        additive—3% of siloxane containing masterbatch. (Masterbatch        concentration 50% siloxane additive, 50% low density        polyethylene carrier polymer).

The composition of the artificial grass carpets was ⅝″ tufting gauge, 60mm pile height at a stitch rate of 21-22 stitches/10 cm.

These grass carpets were then tested with increasing infill rates toassess the effects of free pile height.

All carpets had a stabilising base infill layer 12 a: sand 34 kg/m 2approximately ≈22 mm.

The following infill rates refers to the performance SBR crumb rubberinfill 12 b.

Approx. Infill Depth≈Equivalent Free Yarn Pile Height

31 mm Low 3.33 kg/m²  7 mm 31 mm Mid 6.67 kg/m² 15 mm 23 mm High   10kg/m² 20 mm 18 mm

Testing

To develop insights into the skin injury risk between the control carpetand the carpet produced with yarn containing the slip additive, thefollowing parameters were assessed:

-   -   1) Sliding Coefficient of Friction.    -   2) Deceleration after initial impact/Change in Horizontal        Velocity.    -   3) Simulated Skin Abrasion.    -   4) Rotational Resistance.

Test Methods

Simulated Skin Abrasion Testing—The test apparatus/device 400, shown inFIG. 7 , recreates a realistic knee-turf contact whilst monitoringtemperature rises and the abrasive nature of turf. A horizontal impactvelocity of 5 m/s was generated by adopting roller coaster technology. Alinear induction motor rapidly accelerates a carriage up to the desiredvelocity by utilising electromagnets which provides the ability tomonitor the natural deceleration of the impactor. The impactor was 3Dprinted, using anthropometric knee data, and wrapped in Lorica® Softartificial skin. Lorica® Soft employs polyurethane and polyamidemicrofibres to produce a synthetic leather to provide similar frictionalresponses as hairless skin.

Lorica® artificial leather consisting of polyamide microfleece coatedwith polyurethane has been shown to realistically simulate human skinfriction against textiles under dry conditions. In addition to frictionproperties, the Lorica® skin model reproduces surface properties ofhuman skin (roughness, topography, water contact angle) and showssimilar force-deformation characteristics.

Accelerometers capture impact and dynamic frictional coefficients.Photographs are taken of this artificial skin after the deceleration and% abrasion damage calculated from grey scale images of the artificialskin samples.

Referring to FIG. 7 the test apparatus 400 comprises a test rig whichaims to replicate a lifelike knee slide on an artificial turf surface 10with the new 2-layer skin attached to the knee form.

The rig has a propulsion phase followed by a measurement phase. In thepropulsion phase a realistic velocity and loading is applied.

Stage 1 of the test is acceleration. Stage 2 of the test is the kneedrop. Stage 3 of the test is the impact. Stage 4 of the test is theslide.

In stages 2 and 3, the force experienced in the Y and Z axis (impact anddirection of travel) is measured.

In stage 4, the temperature profile during constant contact with theartificial grass surface and the simulant skin and the COF is measured.

After the test is complete the Lorica® samples were flattened to give aflat surface that can be photographed. These photographs were thenconverted to greyscale threshold abrasion images and the % coverage ofdamage calculated.

Sliding Coefficient of Friction—The coefficient of friction (COF) is theratio of the frictional forces resisting motion to the normal forcepressing the two surfaces together. This is a dimensionless value whichdescribes the relationship between the horizontal and vertical forces oftwo surfaces in relative motion where the literature associates a highCOF value with an increased risk of abrasive injuries. This was measuredon the above test equipment.

Deceleration after initial impact/Change in HorizontalVelocity—Deceleration on the above equipment was measured using animpactor mass was 39.22 kg which would represent a static normal load of385N. A high change in horizontal velocity represents an interactionthat experiences the greatest deceleration between the initial impactand the end of the slide—which would suggest a player on that surfacewould be more vulnerable to receiving a skin injury. Deceleration ismeasured in metres/second.

Rotational Resistance—FIFA Quality Programme for Football Turf Handbookof Test Methods—Test Method 6. Traction between a sports shoe and theplaying surface influences a players' ability to perform sport-specificmovements. Too little traction means a player might slip. Too muchtraction is thought to increase the risk of injury due to foot fixationon the turf. The rotational resistance of a surface is defined as thetorque measured using a torque wrench when a loaded foot is allowed tohorizontally rotate when in contact with the surface. The test foot is ametal disc 150±2 mm with 6 football studs equally spaced on theunderside each 46±1 mm from the centre of the disc. The total mass ofthe apparatus (test foot, shaft, torque wrench and weights) is 46±2 Kg.The weighted test foot is dropped onto the surface from a height of 60±5mm and the torque wrench is attached. Then, without adding any verticalpressure on the torque wrench and applying minimum rotational torque tothe torque wrench, turning the wrench and the test foot smoothly at anominal speed of rotation of 12±2 rev/min until movement of the testfoot occurs and it has rotated through at least 45°. The maximum valuedisplayed on the torque wrench is recorded to the nearest Nm.

Test Data Sliding Coefficient of Friction

Low Infill Mid Infill High Infill Level Level Level Control artificial1.10 0.83 0.72 grass carpet Grass carpet 0.98 0.94 0.72 containing slipadditive (the invention)

The greater the coefficient of friction, the greater the resistance theartificial grass carpet is offering to the player sliding over itssurface and the greater the possibility of an abrasion skin burn. Thelower coefficient of friction observed as infill rate increases isconsistent with the ‘ball bearing effect’, where the increasing level ofinfill rolls over itself offering a lubricating effect to the playersknee sliding across its surface. The lowest infill rate represents aturf sample with the longest free pile height (˜31 mm) and is the samplewhere the maximum amount of yarn containing the slip additive is exposedto the skin, hence having the greatest effect on reducing the slidingcoefficient of friction, reducing resistance offered by the pitch to aplayer sliding over its surface and hence minimising abrasion burns.This demonstrates that the introduction of a slip additive into the testyarn is making a positive contribution to reduction in abrasion skinburns.

% Simulated Skin Abrasion Testing

Low Infill Mid Infill High Infill Level Level Level Control artificial1.73% 10.6% 5.50% grass carpet Grass carpet 0.51% 8.91% 4.35% containingslip additive (the invention)

This data clearly shows the lower skin abrasion damage experienced withthe carpet containing the slip additive—i.e., the invention.

Deceleration after Initial Impact/Change in Horizontal Velocity

Low Infill Mid Infill High Infill Level Level Level Control artificial2.07 m/sec 2.02 m/sec 1.91 m/sec grass carpet Grass carpet 2.01 m/sec1.96 m/sec 1.86 m/sec containing slip additive (the invention)

The greater the change in horizontal velocity, the greater thedeceleration of the players knee on the grass carpet, the greater theresistance offered by the carpet to the player and, therefore, thegreater the chances of skin abrasion

A consistent trend of decreasing change in velocity was observed forincreasing infill rates on both surfaces. This is consistent with the‘ball bearing effect’ where the infill rolls over itself offering alubricating effect to the player's knee sliding across its surface. Thelowest infill rate represents a turf sample with the longest free pileheight (˜31 mm) which corresponds to the highest reduction in speed.This is the sample where the maximum amount of yarn containing the slipadditive is exposed to the skin, hence having the greatest effect onreducing horizontal velocity of the player on the pitch, hence reducingits deceleration, reducing resistance of the pitch and hence minimisingabrasion burns. For each infill rate, the change in speed (and henceabrasion) was always greater for the control sample than for the yarncontaining the slip (siloxane) additive.

Rotational Resistance

Carpets were tested at the high level of infill and after fifty (50)conditioning rolls with a heavy studded roller, such were laid on aSchmitz ProPlay 20 shockpad for test.

High Infill Level Control artificial 39 Nm grass carpet Grass carpet 37Nm containing slip additive (the invention)

The specification for professional levels of play at the time of writingis 32-43 Nm. Both samples meet the requirement, and the samplecontaining the additive (the invention) allows the stud to release withmore ease compared to the control sample. This demonstrates thatalthough the invention gives a more lubricating feel, it does not affectthe grip or traction between the player and the surface and, therefore,meets current safety standards. The lower value achieved by the grasscarpet containing the slip additive allows easier release of the spotsshoe—which will reduce the prevalence of the studs getting stuck in thepitch and hence reduce the risk of lower limb injury.

Referring now to FIGS. 8 and 9 , there will be described a material oryarn, generally designated 5′, for an artificial surface 10′, such as asports surface, for example, a sports playing surface, according to afurther embodiment of the present invention. Like parts of the furtherembodiment are denoted by the same numerals as the preceding embodiment,but suffixed “′”. Also, the composition of the yarns 5′ is the same asthat of the yarns 5.

FIG. 8 shows a schematic perspective view of a plurality of blades,filaments or yarns 5 a comprising a tuft of synthetic grass according tothe further embodiment of the present invention.

FIG. 9 shows a perspective view from above and to one side of theartificial surface/grass/turf 10 a comprising a plurality of tuftsaccording to FIG. 8 . The artificial surface 10′ comprises a (primary)backing material 15′ to which the blades or yarns 5′ are woven ortufted.

In this embodiment, the artificial surface 10′ is provided with aninfill material(s), In the embodiment of FIG. 6 , the infill material(s)are an upper layer of crumb rubber 12 b and a lower layer of sand 12 a.However, in the embodiment of FIG. 9 , the infill material 12′ istexturised yarns or filaments 13′. Beneficially, the texturised yarns13′ are formed from a same material as the material or yarn 5′. Thetexturised yarns 13′ or filaments are woven or tufted to the backingmaterial 15′.

It will be appreciated that the embodiments of the present inventionhereinbefore described are given by way of example only, and are notmeant to be limiting of the scope of the invention in any way.

It will be appreciated that the present invention may find utility invarious sports, and in particular contact sports, for example:

-   -   Football or soccer;    -   Rugby (e.g., rugby union or rugby league);    -   American football or gridiron;    -   Gaelic football (GAA);    -   Shinty or hurling;    -   Australian rules football.

It will also be appreciated that herein, by “straight yarn” or “straightfilament” is meant a yarn or filament which has a length, e.g., around alength of a blade of grass of a lawn. However, it will be appreciatedthat the “straight yarn” or “straight filament” may be twisted along thelength thereof. The twist may be a left-hand or right-hand twist (Z or Stwist). Typically, the number of twists per meter may be around 20 to 50TPM. Alternatively, the “straight yarn” or “straight filament” may bespiral wrapped. Typically, the number of wraps per meter may be around20 to 60 WPM.

1. An artificial surface comprising a plurality of blades, wherein eachof the blades comprises a material or yarn comprising a synthetic turfor grass yarn comprising a polyolefin or polymer material and at leastone additive comprising a siloxane additive, wherein the artificialsurface has: a pile height of around 20 mm to 75 mm; and/or a tuft gaugeof at least ⅜ inch.
 2. An artificial surface comprising a plurality ofblades, wherein each of the blades is substantially straight andcomprises a material or yarn comprising a polyolefin or polymer materialand at least one additive comprising a siloxane additive.
 3. Anartificial surface as claimed in claim 1, wherein each blade comprises afilament which: is substantially straight or linear; is a monofilamentor a slit film; has a propeller or diamond shaped cross-section; and/orhas a cross-sectional width of around 1.0 mm to 2.0 mm, optionally 1.2mm to 1.5 mm, and a cross-sectional breadth of around 200 μm to 450 μm,optionally 300 μm to 380 μm.
 4. An artificial surface as claimed inclaim 1, wherein the polyolefin or polymer comprises: polyethylene, suchas linear low-density polyethylene (LLDPE); and/or a metallocenecatalysed polyolefin.
 5. An artificial surface as claimed in claim 1,wherein the at least one additive comprises one or more compoundselected from Octamethylcyclotetrasiloxane, Hexamethylcyclotrisilaxane,Decamethylcyclopentasiloxane, Dodecamethylcyclohexasiloxane, andHexamethyldisiloxane (HMDS).
 6. An artificial surface as claimed inclaim 1, wherein the polyolefin or polymer material comprises 80% to 90%of the material or yarn.
 7. An artificial surface as claimed in claim 1,wherein the at least one additive comprises 0.1% to 10% of the materialor yarn, optionally 0.5% to 5%, or around 3% of the material or yarn. 8.An artificial surface as claimed in claim 1, wherein the at least oneadditive comprises or forms an outer layer on the material or yarn or onthe polyolefin or polymer material.
 9. An artificial surface as claimedin claim 1, wherein the artificial surface has a tuft gauge of at least½ inch, optionally at least ⅝ inch, optionally at least ¾ inch.
 10. Anartificial surface as claimed in claim 1, wherein the artificial surfacehas a pile height of around 30 mm to 65 mm.
 11. An artificial surface asclaimed in claim 1, wherein the artificial surface is provided with aninfill material.
 12. An artificial surface according to claim 1, whereina sliding coefficient of friction of the artificial surface is between0.7 and 1.0, optionally around 0.94.
 13. An artificial surface accordingto claim 1, wherein the artificial surface is a contact sports playingsurface.
 14. An artificial surface according to claim 1, wherein theartificial surface is an artificial grass surface.
 15. A method offorming an artificial surface according to claim 1, the methodcomprising: providing the material or yarn; tufting the material or yarnto a primary backing or substrate.